The present invention concerns a device for venting a fuel tank, notably for a motor vehicle.
The purpose of venting the fuel tank of a motor vehicle is to prevent any overpressure or negative pressure in the tank. A device for opening to atmosphere is thus provided on the tank in order to preserve a reasonable internal pressure in it, whatever the external temperature and altitude at which the tank is situated.
The tank is thus prevented from deforming significantly, notably under negative pressure.
Thus, as the tank gradually empties of its fuel, it is necessary to admit air inside the tank in order to prevent the pressure from dropping excessively. On the other hand, when the reservoir is exposed to a high rise in temperature, for example when the vehicle is parked in the sun, the vapour pressure contained in the tank can increase greatly and it is then necessary to discharge some of these vapours to the outside.
In addition to this function of venting the tank, it is also necessary to provide means for preventing the fuel being able to emerge through the device for venting when the level of fuel close to this device increases significantly, for example following acceleration undergone by the vehicle, or if this vehicle turns over.
A device for venting a fuel tank is known, as described in the French patent application FR 98 06727, which has a chamber communicating on the one hand with the tank and on the other hand, through an outlet orifice, with a pipe for opening to atmosphere.
In order to provide a system for preventing leakage of fuel under all running conditions, and if necessary when the vehicle turns over, this device for venting has a float, housed in a chamber, adapted to force a needle upwards when the level of fuel reaches the device, the needle then closing off the orifice so as to prevent any leakage of fuel to the outside.
As illustrated in FIG. 1, such a device for venting is generally incorporated in a top wall 11 of the fuel tank 2.
The device for venting thus occupies the space separating the fuel tank 2 from the chassis 3 of the vehicle.
In addition, a minimum distance G must separate the bottom of the tank 2 from the ground 4.
Finally, a safety distance m is provided between the device for venting 1 immersed in the tank 2 and the maximum level M of fuel in this tank when the vehicle is stopped.
These technical constraints related to the mounting of the reservoir 2 in the vehicle, between the chassis 3 and ground 4, limit the space available for the device for opening to atmosphere.
The purpose of the present invention is notably to reduce the overall bulk of a device for venting a fuel tank.
To this end, the present invention relates to a device for venting a fuel tank having a chamber communicating on the one hand with the tank and on the other hand, through an outlet orifice, with a pipe for opening to atmosphere, and a float, housed in the chamber, having an external skirt delimiting an internal space in the float and a needle adapted to close off the outlet orifice when the fuel level exceeds a predetermined threshold in the chamber.
In accordance with the invention, the float has at least one partition adapted to divide up the internal volume of the float, with a height substantially equal to the height of the external skirt.
This internal partitioning of the float thus increases the useful flotation volume when the surface of the fuel in contact with the float is no longer strictly horizontal in the reservoir, that is to say during acceleration or braking phases or when the vehicle is going round bends, climbing or descending.
This is because the operation of the float is assured by virtue of the internal volume of this float capable of containing a gaseous volume coming from the emanation of fuel vapours.
By increasing the useful flotation volume, it is possible to reduce the overall height of the float, for an external skirt diameter equivalent to the usual diameter.
By thus reducing the height of the float, the overall bulk of the device for venting is also reduced along with the space necessary for fitting it between the vehicle chassis and the tank.
According to a preferred characteristic of the invention, the external skirt of the float and the partition are concentric.
This partition arrangement thus makes it possible to divide up the internal volume of the float in all directions around its axis of movement.
Thus the useful flotation volume in the float is increased whatever the direction in which the level of fuel is sloping in the tank.
According to one advantageous characteristic, the float has several concentric partitions, thus creating several compartments within the float.
Alternatively, according to another characteristic of the invention, the external skirt of the float and the partition are perpendicular, which makes it possible to divide up the internal volume of the float in specific directions.
In a practical embodiment of the invention, the float has a first series of concentric partitions delimiting annular internal volumes in the float, and a second series of partitions, perpendicular to the partitions in the first series and adapted to divide up the annular internal spaces.
The arrangement of partitions, both concentric and perpendicular, makes it possible to increase the number of compartments partitioning the internal space of the float, and thus to increase the useful flotation volume of this float.
The Applicant estimates that it was thus possible to reduce the total height of the float by approximation 30%.
According to a characteristic which is particularly simple to implement, the float has a tubular external skirt and at least one internal tubular partition.
Other particularities and advantages of the invention will also emerge from the following description.